High Voltage distribution grounding?

[NoahsArc]

I'm a simple wireman, I am not sure how this is done typically.

If you have, say, a 150kV line sending power 50km to a distant substation, what sort of setup would be used typically, as in, wye or corner ground delta or ungrounded delta or what?

If grounded, would you bond at both ends of this line?

Thanks

 

[electrofelon]

I'm a simple wireman, I am not sure how this is done typically.

If you have, say, a 150kV line sending power 50km to a distant substation, what sort of setup would be used typically, as in, wye or corner ground delta or ungrounded delta or what?

If grounded, would you bond at both ends of this line?

Thanks

Good question, I've always wondered. I just spent 5 minutes googling it.....lol, a whole bunch of worthless answers. I read someone saying they're almost always delta, then the next one I read is someone saying they are almost all wye. Then the next one I read is someone saying they're nearly all Delta again .... Why can't people just say they don't know? Maybe @Hv&Lv can settle this?

 

[Elect117]

It will depend.

Most voltage classes might be either. For example 480V can be a wye service or a corner grounded service. It more so depends on the transformer.

150kV will most likely warrant a tower, with one or two lightning ground wires run with it. Depending on the physical construction of the circuit.

I don't know of any neutral (4 wire) system that would run at that voltage.

We have a delta 7200 and a wye 16340. I think the wye neutral point is grounded at the transformer but no neutral is ran in the circuit and I don't think the 7200 is grounded at all.

 

[Julius Right]

The high-voltage transmission line is not provided with neutral but with static wire grounded at each tower and at both ends.

 

[mtnelect]

A "Single Point Grounding" would require a grounded wire from the substation to the end of the system. The utilities wouldn't do that because it would be too expensive. So, they went for MNG instead and stuck it to the homeowner.

 

[mtnelect]

That's why we have all this current pumped into the ground by the utilities. So, now the NEC wants the homeowners to pay for installation of a grid system to neutralize the "Stray Current" that they caused. Itis like we have to bond everything with ground rods to protect our homes.

 

[electrofelon]

A "Single Point Grounding" would require a grounded wire from the substation to the end of the system. The utilities wouldn't do that because it would be too expensive. So, they went for MNG instead and stuck it to the homeowner.

OP was referring to transmission not distribution. But note an electrical system can also be ungrounded, it does not have to be grounded at all.

 

[NoahsArc]

The high-voltage transmission line is not provided with neutral but with static wire grounded at each tower and at both ends.

Okay, in this case it is 3 wire. But is one of the legs bonded to ground, or is there a wye with the center tap bonded to ground and unused?

A "Single Point Grounding" would require a grounded wire from the substation to the end of the system. The utilities wouldn't do that because it would be too expensive. So, they went for MNG instead and stuck it to the homeowner.

MNG?

OP was referring to transmission not distribution. But note an electrical system can also be ungrounded, it does not have to be grounded at all.

Yes transmission in this case, but also curious about distribution.

 

[jim dungar]

A "Single Point Grounding" would require a grounded wire from the substation to the end of the system. The utilities wouldn't do that because it would be too expensive. So, they went for MNG instead and stuck it to the homeowner.

I don't know many homeowners that take service at 150kV, as in the OP question.

Not all nationwide POCO designs have been made based solely on the needs of residential customers, many were due to the issues of creating a nationwide interconnected/transparent grid.

 

[NoahsArc]

I'm also not 100% on the voltage, I just know it's transmission-only.
I'll put it this way, what I know is:

• 100MW power plant delivering to a substation
• 30mi away
• 3 wire on poles
• not the giant fancy metal trusswork poles, just tall (20-30ft) wooden ones, if that makes a difference

Probably less than 150kV, I don't know, most I've ever touched is 480.

 

[electrofelon]

Okay, in this case it is 3 wire. But is one of the legs bonded to ground, or is there a wye with the center tap bonded to ground and unused?


MNG?


Yes transmission in this case, but also curious about distribution.

Distribution is a mix. Ungrounded Delta was very popular in some parts of the country. Tons of it in upstate NY, 4800 volts. 12470Y/7200 Multi grounded neutral is probably the most common distribution system in the US, super common. Another real common 15kv class distribution voltage is 13200/7620, also typically used as a multi-grounded neutral. Kind of a guess, but I don't think you will find any new/newer ungrounded distribution lines, they will all be wye multi grounded neutral.

 

[electrofelon]

Distribution typically stops at 35kv. Popular Transmission voltages are typically 69kv, 115kv, 235kv and up, but as I said before I'm not sure about the grounding.

 

[NoahsArc]

Distribution typically stops at 35kv. Popular Transmission voltages are typically 69kv, 115kv, 235kv and up, but as I said before I'm not sure about the grounding.

Well given 100MW and probably max 750A per line, we're looking at 115kV minimum with Vdrop then out of those.

Let me get into the reason I'm asking. I've come across a situation of stray voltage that doesn't have a clear cause. It's a unique geographical situation, where there is the power station along an ocean coast, and a substation 30mi away also along the coast, and a peninsula in the (electrolytic) water between, with the property dead center between the two watersheds of that peninsula.

We're not sure if the stray voltage could be coming from local distribution lines (with the distribution fuse/neutral pulled over 1km away they still have stray voltage on an otherwise fairly isolated piece of grid) or objectionable grounding current from the transmission setup above.
If the transmission system is grounded on both ends and is running at over 100kV, that's about 4kV per mile of Vdrop. In this case, due to the peninsula and the fact the current has to go longways around the peninsula in the water, if there's a point between watersheds that's higher ohms than the rest, it could be seeing 10kV+ potential between one and the other.

I want to know if I'm totally off-base thinking this is the issue rather than a 3km distant distribution fault or objectionable ground current scenario.